Detection Of Redox-sensitive Small Molecules （H₂O₂ And GSH） By 3-hydroxyflavonoid Esipt Fluorescent Probe

Reactive oxygen species （ROS） are produced during metabolism and aerobic oxidation in human and animal organisms. When stimulated by internal or external signals, the increased ROS will lead to oxidative stress, and oxidative stress is thought to be an important factor leading to aging and diseases. Some small molecules can synergistically regulate the redox state of the cells, which is critical to maintain the normal homeostasis of cells. As H₂O₂ was one kind of ROS with relative stability as well as high content, and glutathione （GSH） was the representative reducing species, the detection of intracellular H₂O₂ and GSH can reflect the redox status of cells to some degree, which could be used in the evaluation of the efficacy of antioxidant drugs.In recent years, fluorescence sensors have been widely used in the detection of small molecules in cells. 3-Hydroxychromone （3HC） derivatives are classical fluorescent sensors with excited-state intramolecular proton transfer（ESIPT）mechanism, which have high fluorescence quantum yield, larger Stokes shift, two fluorescence emission peaks.3HC compounds are very sensitive to the polarity of the environment and widely used in the research of biomacromolecule such as nucleic acid, protein and vesicles et al.In this dissertation, 3HC was used as fluorescent group for the designed probes. The results of experiments in solution displayed that the ESIPT effect of 3HC was enhanced and produced two fluorescence emission in the present of bovine serum albumin （BSA）which can provide a hydrophobic microenvironment. Besides, the results of confocal microscopy confirmed that the fluorescent group 3HC also emitted strong emission in cells with rich proteins. Therefore, in order to detect H₂O₂ or GSH, we modified 3HC with boronic acid pinacol ester or 2,4-dinitrobenzenesulfonyl, and obtained 3HC-18-1 and 3HC-19-2, respectively. The detection groups can be cleaved by the target molecules,thus achieving the "Turn-on" type of fluorescence probes. The results showed that both 3HC-18-1 and 3HC-19-2 had the characteristics of high sensitivity and good selectivity,and then could be applied in the detection of H₂O₂ and GSH in Hela cells.In addition, we modified 3HC with the quaternary ammonium methyl pyridine group for the localization of mitochondrial, and obtained a new fluorescent group 3HC-11. The results confirmed that 3HC-11 was able to locate at the mitochondria and emit fluorescence, which was beneficial to develop mitochondrial fluorescent probes.